lkml.org 
[lkml]   [2020]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm: Make mem_cgroup_id_get_many dependent on MMU and MEMCG_SWAP
From
Date
Hi Johannes,

On 3/5/20 4:09 PM, Johannes Weiner wrote:
> On Thu, Mar 05, 2020 at 09:49:23AM +0000, Vincenzo Frascino wrote:
>> Hi Michal,
>>
>> On 3/4/20 4:53 PM, Michal Hocko wrote:
>>> On Wed 04-03-20 14:23:48, Vincenzo Frascino wrote:
>>>> mem_cgroup_id_get_many() is currently used only when MMU or MEMCG_SWAP
>>>> configuration options are enabled. Having them disabled triggers the
>>>> following warning at compile time:
>>>>
>>>> linux/mm/memcontrol.c:4797:13: warning: ‘mem_cgroup_id_get_many’ defined
>>>> but not used [-Wunused-function]
>>>> static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned
>>>> int n)
>>>>
>>>> Make mem_cgroup_id_get_many() dependent on MMU and MEMCG_SWAP to address
>>>> the issue.
>>>
>>> A similar patch has been proposed recently
>>> http://lkml.kernel.org/r/87fthjh2ib.wl-kuninori.morimoto.gx@renesas.com.
>>> The conclusion was that the warning is not really worth adding code.
>>>
>>
>> Thank you for pointing this out, I was not aware of it. I understand that you
>> are against "#ifdeffery" in this case, but isn't it the case of adding at least
>> __maybe_unused? This would prevent people from reporting it over and over again
>> and you to have to push them back :) Let me know what do you think, in case I am
>> happy to change my patch accordingly.
>
> I would ack a patch that adds __maybe_unused.
>
> This is a tiny function. If we keep it around a few releases after
> removing the last user, it costs us absolutely nothing. Eventually
> somebody will notice and send a patch to remove it. No big deal.
>
> There is, however, real cost in keeping bogus warnings around and
> telling people to ignore them. It's actively lowering the
> signal-to-noise ratio and normalizing warnings to developers. That's
> the kind of thing that will actually hide problems in the kernel.
>
> We know that the function can be unused in certain scenarios. It's
> silly to let the compiler continue to warn about it. That's exactly
> what __maybe_unused is for, so let's use it here.
>

I agree with what you are saying. I am going to change my patch accordingly.

Thank you.

--
Regards,
Vincenzo

\
 
 \ /
  Last update: 2020-03-05 17:21    [W:0.077 / U:0.792 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site